We have investigated the interaction of lipoproteins with liposomes to form recombinant particles. A number of lipoproteinfractions (VLDL, IDL, LDL, and HDL) all disrupt liposome structure by an essentially irreversible and quasistoichiometric process. In the case of HDL, the major apoprotein, A-I, recombines with dimyristoyl choline vesicles to form discs approximately 100 A in diameter and 32 A in thickness, with protein on the rim. These structural results were obtained by a combination of neutron scattering, electron microscopy, and column chromatography.